# CallbackManagerMixin

> **Class** in `langchain_core`

📖 [View in docs](https://reference.langchain.com/python/langchain-core/callbacks/base/CallbackManagerMixin)

Mixin for callback manager.

## Signature

```python
CallbackManagerMixin()
```

## Methods

- [`on_llm_start()`](https://reference.langchain.com/python/langchain-core/callbacks/base/CallbackManagerMixin/on_llm_start)
- [`on_chat_model_start()`](https://reference.langchain.com/python/langchain-core/callbacks/base/CallbackManagerMixin/on_chat_model_start)
- [`on_retriever_start()`](https://reference.langchain.com/python/langchain-core/callbacks/base/CallbackManagerMixin/on_retriever_start)
- [`on_chain_start()`](https://reference.langchain.com/python/langchain-core/callbacks/base/CallbackManagerMixin/on_chain_start)
- [`on_tool_start()`](https://reference.langchain.com/python/langchain-core/callbacks/base/CallbackManagerMixin/on_tool_start)

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[View source on GitHub](https://github.com/langchain-ai/langchain/blob/c59e83a1ffba63d709ea4847445845edd82085dc/libs/core/langchain_core/callbacks/base.py#L238)